Air filter having ductile metal frame



Dec. 20, 1966 R. J. cu'rA AIR FILTER HAVING DUCTILE METAL FRAME 3Sheets-Sheet 1 Original Filed Jan. 14, 1963 7v I V o" V R I Roarnr J Cumfink-11$ 'F Siarke I A'fforneys Dec. 20, 1966 R. J. CUTA 3,

AIR FILTER HAVING DUCTILE METAL FRAME Original Filed-Jan. 14, 1963 5Sheets-Sheet 2 INVENTOR' ROBERT 0: Cam

A 1 for-ney:

Dec. 20, 1966 R. J. CUTA 3,292,349

AIR FILTER HAVING DUCTILE METAL FRAME Original Filed Jan. 14, 1963 5Sheets-Sheet 5 IIIIIIIII J'II VIIIIIIIIII INVENTOR 8085a? I Cum Y L BY Qfndrus Shirk:

Attorneys resistance to separation from the filter media.

United States Patent 3,292,349 AIR FILTER HAVING DUCTILE METAL FRAMERobert J. Cuta, Madison, Wis., assignor to Research ProductsCorporation, Madison, Wis., a corporation of Wisconsin Continuation ofapplication Ser. No. 251,164, Jan. 14, 1963. This application Sept. 22,1965, Ser. No. 497,583 8 Claims. (Cl. 55511) This application is acontinuation of application Serial No. 251,164, filed Ian. 14, 1963, andentitled Improved Filter and Frame, which became abandoned subsequent tothe filing of the present application.

This invention relates to an improved filter and frame, and moreparticularly to a novel construction for air filters and the likewherein an improved frame construction is utilized.

In the art of manufacturing relatively rigid and/ or flexible airfilters commonly used in heating, ventilating, air conditioning or thelike, it is often desirable to include a peripheral frame secured to thefilter edge. Such frames provide, among other things, support andprotection for the filter, thereby prolonging filter life and providingimproved appearance. The frame also facilitates mounting of the filtersecurely in the air stream path so that the edges thereof are air tight.

Filter bodies of the type suitable for framing may be of the type shownin US. Patent No. 2,754,928. That shown is of interstitial design andhas broad ingress and egress faces comprised of a plurality ofsuperposed layers of flexible, open-mesh slit and expanded sheetmaterial, such as aluminum foil. Reference is also made to US. PatentNo. 2,070,073 which shows a filter body of superposed expanded sheets.

The present invention is applicable to filtering media of expandedaluminum foil and othermaten'als such as expanded copper foil, wire orwire-like strands of reasonably malleable metal felted, knitted orotherwise formed into a filtering body. Fiber glass media, open cellularplastic foam, stacked corrugated wire mesh screens and stacked chainstitched mesh media are also suitable.

Heretofore, problems have arisen in connection with the construction offilters of the general type indicated above, wherein a supporting frameenvelops the peripheral edge .of the filter media. It has been foundespecially with elongated filters, that the frame was not alwayssufiiciently anchored to the elongated edge of the filter media, andwould on occasion substantially separate therefrom. In addition,previous attempts to form a framed filter to various contoured shapeshave met with failure because the stresses involved have increased theseparation and have caused unsightly and undesirable wrinkling of theframe itself, unless the metal frame is of extremely heavy gauge.

The present invention solves the aforementioned problems and provides aconstruction wherein a frame of comparatively light stock will notwrinkle or separate from the filter media, even when the filter issubsequently bent in the form of compound and sharp curvatures.

Generally, the invention is based on utilizing a frame which is formedto provide several areas of mechanical In the major embodiment of theinvention, the edge portions of both frame legs are bent in the samedirection and extend at an angle to the general plane of the filter andframe.

ice

The accompanying drawings illustrate the best mode presentlycontemplated-by the inventor for carrying out the invention.

In the drawings:

FIGURE 1 is a perspective view of a generally elongated filterconstructed in accordance with one embodiment of the invention;

FIG. 2 is an enlarged fragmentary section of the completed filterassembly, taken on line 22 of FIGURE 1;

FIG. 3 is an enlarged fiagmentary perspective view of a frame assembledto a filter prior to anchoring it thereto;

FIG. 4 is an enlarged view similar to FIG. 2, and illustrating themembers for forming the frame to its final shape;

FIG. 5 is a perspective view of a modified form of the embodiment of theinvention shown in FIGS. 14;

FIG. 6 is a perspective view of still another modification of theembodiment of the invention shown in FIGS. 14;

FIG. 7 is a perspective View of still another modification of theembodiment of the invention shown in FIGS. 14;

FIG. 8 is a perspective view of yet another modification of theembodiment of the invention shown in FIGS. 14;

FIG. 9 is a perspective view of another modification of the embodimentshown in FIGS. 1-4;

FIG. 10 is an enlarged section, similar to FIG. 2, of a secondembodiment of the invention;

FIG. 11 is an enlarged section, similar to FIG. 2, of a third embodimentof the invention;

FIG. 12 is a plan view of a framed assembly having a plurality ofsections and utilizing a modified form of the embodiment shown in FIG.2;

FIG. 13 is an enlarged section taken on line 13'-13 of FIG. 12;

FIG. 14 is an enlarged section similar to FIG. 10 and showing amodification thereof; and

FIG. 15 is an enlarged section similar to FIG. 11 and showing amodification thereof.

As shown in FIGS. 1 and 2 of the drawings, the invention may be embodiedin an air filter comprising an elongated filter media body 1 oflightweight single or multilayer construction. The edge of body 1 isenclosed or envelopedby a generally channel-shaped ductile metal rim orframe 2 which includes an upper leg 3 and a lower leg 4 spacedtherefrom.

As shown, frame 2 may comprise a plurality of separate elements witheach element extending along one edge of the filter body and joined toadjacent elements at the corners in any suitable manner, such as thatdisclosed in the present inventors copending patent application Ser. No.209,679, filed July 13, 1962 and entitled Locking Method and ProductObtained Thereby, now Patent No. 3,252,213, and assigned to a commonassignee. A1- ternatively, frame 2 may be made in a single piece andbent at the corners, such as in US. Patent No. 882,397 issued Mar. 17,1908.

In accordance with the invention, and as shown in FIG. 3, the frameelements are formed from a strip of aluminum or the like and areinitially bent over to provide open legs. These frame elements areplaced loosely over the generally planular edges of the filter body. Inmany instances, as when the filter body is of substantial thickness,such as /2" to 2", it is necessary to precompact the filter edge so thatit properly fits within the legs of the frame. This pre-compaction maybe accomplished in any suitable manner, such as is shown in FIG. 3 ofthe drawings of copending John A. Liebmann application Ser. No. 81,842,filed Jan. 10, 1961, entitled Method of Framing a Filter and ProductObtained thereby and assigned to a common assignee which was copendingwith original application Ser. No. 251,164 referred to above, and whichis now abandoned,

In the case of plastic foam filter media, thickness reduction can beaccomplished by hot pressing at the margins, or treating them with athermoplastic or resinous hot setting composition to hold the margins ina compressed form while they are inserted into the frame.

The entire assembly is then placed in a suitable forming mechanism whichincludes (FIG. 4) an upper male die 5 and a lower female die 6 which arecontoured to produce the final frame shape. 'Actuation of the formingapparatus serves to form the legs 3 and 4. When the filter body edge hasnot been precompacted, forming as in FIG. 4 also compacts the edge 7 ofbody 1 so that it is substantially thinner than the remaining centralbody portion.

As best shown in FIGS. 2 and 4, frame 2 has a hairpin-like cross sectionand the legs serve to confine filter edge 7 therebetween. For thispurpose, each leg is provided with outer and inner edge areas joined bya central body segment.

As best shown in FIG. 4, the central body segment of upper leg 3comprises a generally flat inner portion 8 which merges outwardly intoan outer portion 9 which is upwardly inclined at an acute angle toportion 8. The point of merger between portion 8 and converging portion9 provides a slight inner ridge or shoulder 10 which provides an abruptchange in direction of leg extent for purposes to be described. Flatportion 8 is disposed parallel to the general plane of a fiat frame orto the axis of curvature of the respective portion of a contoured frame.

The central body segment of lower leg 4 comprises a generally flatportion 11 which is disposed parallel to flat portion 8 and whichextends beneath both portions 8 and 9 and to slightly inwardly of theformer.

Leg portions 9 and 11 merge outwardly into the outer edge area of theframe which joins them and which comprises a generally arcuate. fold 12having a radius of curvature about equal to the distance between flatportions 8 and 1 1.

Further in accordance with the major embodiment of the invention, legportions 8 and 11 merge inwardly into the inner edge areas of the frame.For this purpose, leg 8 merges into a flange 13 which is upwardlyinclined at a substantial angle thereto, such as about 45. The junctureof leg portion 8 and flange 13 produces an inner ridge or shoulder 14.In addition, flat portion 11 merges into a flange 15 which is upwardlyinclined at a greater angle than flange 13 so that it converges with thelatter. The juncture between portion 11 and flange 15 provides an innervalley 16 which provides an abrupt change in leg extent. Flange 15 isprovided with a lip 17 which is inclined at an angle less than flange13, so that it gradually diverges from the latter. The juncture betweenflange 15 and lip 17 provides an inner n'dge or shoulder 18. Filter edge7 is tightly confined between all' the elements of the frame andsubstantially fills the'space therebetween. The outer extremity of edge7 is gradually reduced in thickness toward the confined area betweenfiat portions 8 and 11. The edge is of constant 4 by the edge corners 19and 20 of flange 13 and lip 17 respectively and hence merges into thefilter body proper.

Thus, filter edge 7 is so formed by frame 2 that it alternately changesthickness, starting from the outer extremity: from decreasing toconstant to increasing to decreasing, and finally to increasing section.In addition the general direction of edge extent is substantiallychanged within the frame inwardly of the portion of constant thickness,i.e., at shoulder 14.

Shoulders 10, 14 and 18 which are disposed at three points wherein thethickness alternates, provide substantial mechanical resistance tolateral separation of the frame and filter. Any component of lateralforce tending to cause separation will be strongly resisted, since theedge 7 will have to pull past the shoulders.

In addition, since flanges 13 and 15 and lip 17 all extend in the samegeneral direction from the frame legs and at an angle thereto,separation is retarded by the abrupt change in general extent of thecentral filter body at point 14 and at corner 20. The filter must alsopass over the corner 20 which thereby provides further resistance.

While the filter shown in FIG. 1 is flat, the invention can be adaptedwith advantage to many different configm rations.

In FIG. 5, the elongated filter is shown as having three sharp laterallyextending parallel bends 21. The inventor has found that the frametenaciously holds the width of the filter within the acceptedmanufacturing tolerances and does not wrinkle appreciably even thoughbent sharply at or more. Other known frames would tend to spread and letthe filter media slip out. This filter is adaptable for ventilation ofelectronic devices such as computers and the like. modernistic airconditioners and in cramped quarters.

FIG. 6 shows a construction wherein the filter has. a double curvaturewith all of the curve elements parallel.

Here, again, no separation occurs. The ductility of this i relativelylight gauge metal frame permits this compound curvature.

FIG. 7. shows a construction wherein one elongated edge 22 has a sharpercurvature than the opposite edge 23. Edge 23 can even be straight andthe frame will still cling to the filter.

In FIG. 8, the filter has been formed into a cylinder with the endssecured together as by staples 24. Such a filter illustrates theremarkable facility with which the frame may be curved withoutdistortion. The filter may be used for air supply of internal combustionengines.

In some instances, it is desirable to utilize a filter where-':

in the frame does not extend around the entire periphery of the filter,but rather only along one or several sides.

FIG. 9 shows an elongated filter having the frame elements 25 of theinvention extending only along the long edges, with no frame along theshort ends. Such a filter may have a curved transverse section, asshown, and is useful in computing machines or in other suitableapplica-.

tions.

FIG. 10 shows an embodiment slightly different than.

the major embodiments of FIGS. 1-9. This frame ele ment may, as with theother embodiments, be adapted thereby forming a further valley 27therebetween.

end of extension 26 which provides resistance similar to corner 20 ofFIG. 4.

A further embodiment is shown in FIG. 11 wherein the frame of FIGS. l-9is modified by eliminating flange 13 and lip 17. In this instance, flatportion 8 terminates in an edge 29 and flange 15 terminates in an edge30 above edge 29. The annular flange 15 combined with the horizontalportion' 8 provides a resistance to separation,

since the filter media must pull upwardly at edge 29 and It may also beused in i then over edge 30. The filter media may increase in thicknessinwardly of the latter edge.

FIGS. 12-15 show structures wherein the various embodiments of theinvention may be utilized in a sectionalized filter having filter mediain one section and another material, such as translucent plastic, in theother section. Such assemblies have found uses in certain airconditioning applications utilizing a combined framed filter and window.

As shown generally in FIG. 12, the assembly comprises a peripheral frame31 which may be at least partially of the type of the present invention.A cross-brace 32 joins opposite edges of the frame and joins a suitablefilter media body 33 in the lower section and a clear planular window 34in the upper section.

As shown in FIG. 13, cross brace 32 is similar to the frame of FIGS. l-9for securing body 33. However, in addition, lower leg 4 becomesintermediate and is folded back upon itself at its inner end and isextended outwardly to form a third leg 35 which is generally coextensivewith and spaced beneath leg 4. This space is adapted to receive window34, which extends outwardly of crossbrace 32.

FIG. 14 shows a cross-brace 36 similar to the frame shown in FIG. 10.Here again, the lower leg is folded back upon itself to form a third leg37 spaced to receive the window 34.

Finally, FIG. shows a cross-brace 38 similar to the frame shown in FIG.11. The lower leg is also folded back upon itself to form the third leg39 spaced to receive window 34.

The invention provides an outstanding improvement in the art of framedfilters. By laterally alternating the thickness of the frame betweenspaced frame portions, and by radically altering the direction oflateral extent of the filter edge, the final product will not pull apartor separate. Nor will it distort upon bending.

The filter media is gripped by the frame behind one or more pocketsfilled with the media. The outer pocket is formed in a loop area whichenables a limited amount of flexing or curving of the frame.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim: 1

1. A framed filter comprising, a filter media body of crushable materialof substantial thickness and having a peripheral edge portion, and aductile channel-like metal frame enveloping and compacting at least partof said edge portion therebetween and comprising an upper leg spacedfrom a lower leg and with said legs joined along the outer edges thereofby an arcuate fold, said upper leg converging toward said lower leginwardly from said arcuate fold and forming a first shoulder at theinner end of the convergence and providing an enlarged pocket in theregion of said arcuate fold, both said legs extending in parallelrelationship inwardly of said-first shoulder and with said upper legproviding a second shoulder disposed inwardly of the first shoulder,said legs converging at a substantial angle to and inwardly of theparallel portions thereof, and with said lower leg providing a thirdshoulder at the inner end of such last-named convergence,

said legs diverging inwardly from said third shoulder and with saidlower leg terminating at an edge over which said filter media body isdisposed, the edge portion of said media being confined in said frameand substantially filling the space between said legs and in said fold,and the structure providing mechanical resistance to lateral separationof the frame from said body.

2. The framed filter of claim 1 in which said lower leg along at leastone side of the frame is folded back upon itself at its inner end toprovide a third leg generally coextensive with and spaced from saidlower leg, and a sheet of material disposed in the space between saidlower leg and said third leg and extending outwardly away from saidfilter media body.

3. A framed filter comprising, a filter media body of crushable materialof substantial thickness and having a peripheral edge portion, and aductile channel-like metal frame enveloping and compacting at least partof said edge portion therebetween and comprising an upper leg spacedfrom a lower leg and with said legs joined along the outer edges thereofby an arcuate fold, said upper leg converging toward said lower leginwardly from said arcuate fold and forming a first shoulder at theinner end of the convergence and providing an enlarged pocket in theregion of said arcuate fold, both said legs extending in parallelrelationship inwardly of said first shoulder and t with said upper legproviding a second shoulder disposed inwardly of the first shoulder,said legs converging at a substantial angle to and inwardly of theparallel portions thereof, and with said lower leg terminating at theinner end of said last-named convergence at an edge over which saidfilter media body is disposed, said upper leg providing a horizontaledge portion extending inwardly from the inner end of said last-namedconvergence, the edge portion of said media being confined in said frameand substantially filling the space between said legs and in said fold,and the structure providing mechanical resistance to lateral separationof the frame from said body.

4. The framed filter of claim 3 in which said lower leg along at leastone side of the frame is folded back upon itself at its inner end toprovide a third leg generally coextensive with and spaced from saidlower leg, and a sheet of material disposed in the space between saidlower leg and said third leg and extending outwardly away from saidfilter media body. t

5. A framed filter comprising, a filter media body of crushable materialof substantial thickness and having a peripheral edge portion, and aductile channel-like metal frame enveloping and compacting at least partof said edge portion therebetween and comprising an upper leg spacedfrom a lower leg and with said legs joined along the outer edges thereofby an arcuate fold, said upper leg converging toward said lower leginwardly from said arcuate fold and forming a shoulder at the inner endof the convergence and providing an enlarged pocket in the region ofsaid arcuate fold, both said legs extending in parallel relationshipinwardly of said shoulder and with said upper leg terminating at a firstedge inwardly of the said shoulder, the inner portion of said lower legextending upwardly at an angle from the parallel portion thereof andterminating at a second edge disposed above. said first edge and overwhich said filter media body is disposed, the edge portion of said mediabeing confined in said frame and substantially filling the space betweensaid legs and in said fold, and the structure providing mechanicalresistance to lateral separation of the frame from said body.

6. The framed filter of claim 5 in which said lower leg along at leastone side of the frame is folded back upon itself at its inner end toprovide a third leg generally coextensive with and spaced from saidlower leg, and a sheet of material disposed in the space between saidlower leg and said third leg and extending outwardly away from saidfilter media body.

7. A framed air filter adapted to be bent into any one of a plurality ofshapes, said filter having a generally planar filter media of crushablematerial of substantial thicknessproviding peripheral edge portions anda duotile metal frame facilitating flexing with a minimum of distortionand enveloping and compacting said edge portions, said frame comprisingside members having an upper leg and a lower leg closely confining andgripping the corresponding edge portions of said filter media, and anoutwardly curved loop joining said legs at the outer marginal edge ofthe frame with said legs converging inwardly of said loop toadditionally crush the filter media inwardly of said loop to a thicknesssubstantially less than its original thickness and substantially lessthan the thickness of the filter media in said loop, said legs formingan enlarged pocket substantially filled with the edge portions of saidfilter media to prevent separation of. the same from the frame uponbending of the filter.

8. The construction of claim 7 in which said legs have their inner edgesformed angularly of the general plane of the filter and are related toeach other angularly to provide at least one additional pocket forfilter media extending generally parallel to the frame members andproviding areas of compacted filter media of different thicknesses anthereby tending to additionally prevent separation of the filter mediafrom the frame upon bending.

References Cited by the Examiner UNITED STATES PATENTS Bracher 55-521 XI Limoge 160-402 X Everhard 160-371 X I Abronski 160-399 X I Broudy eta1. 55-504 X Somers 55-491 X Sullivan et al. 210-499 X Hartman.

ROBERT F. BURNETT, Primary Examiner.

7. A FRAMED AIR FILTER ADAPTED TO BE BENT INTO ANY ONE OF A PLURALITY OFSHAPES, SAID FILTER HAVING A GENERALLY PLANAR FILTER MEDIA OF CRUSHABLEMATERIAL OF SUBSTANTIAL THICKNESS PROVIDED PERIPHERAL EDGE PORTIONS ANDA DUCTILE METAL FRAME FACILITATING FLEXING WITH A MINIMUM OF DISTORTINAND ENVELOPING AND COMPACTING SAID EDGE PORTIONS, SAID FRAME COMPRISINGSIDE MEMBERS HAVING AN UPPER LEG AND A LOWER LEG CLOSELY CONFINING ANDGRIPPING THE CORRESPONDING EDGE PORTIONS OF SAID FILTER MEDIA, AND ANOUTWARDLY CURVED LOOP JOINING SAID LEGS AT THE OUTER MARGINAL EDGE OFTHE FRAME WITH SAID LEGS CONVERGING INWARDLY OF SAID LOOP TOADDITIONALLY CRUSH THE FILTER MEDIA INWARDLY OF SAID LOOP TO A THICKNESSSUBSTANTIALLY LESS THAN ITS ORIGINAL THICKNESS AND SUBSTANTIALLY LESSTHAN THE THICKNESS OF THE FILTER MEDIA IN SAID LOOP, SAID LEGS FORMINGAN ENLARGED POCKET SUBSTANTIALLY FILLED WITH THE EDGE PORTIONS OF SAIDFILTER MEDIA TO PREVENT SEPARATION OF THE SAME FROM THE FRAME UPONBENDING OF THE FILTER.